1. The Field of the Invention
The present invention relates to polyaxial and fixed bone screws and components thereof that can be used for stabilizing adjacent vertebrae of the spine or other adjacent bones.
2. The Relevant Technology
Polyaxial screws are commonly used in spinal operations for adjusting or stabilizing adjacent vertebrae. For example, in one conventional procedure a first polyaxial screw is screwed into a first vertebra while a second polyaxial screw is screwed into an adjacent second vertebra. A stabilizing rod is then secured between the polyaxial screws so as to fix the adjacent vertebrae relative to each other. Polyaxial screws can be positioned on each side of each vertebra and can be positioned in any number of consecutive vertebrae with one or more rods extending between the different polyaxial screws.
A conventional polyaxial screw comprises a bone screw having a collar pivotably mounted on the end thereof. The bone screw is inserted into the bone and the stabilizing rod is received within the collar and secured therein. To be strong enough to handle the stresses placed upon it, the polyaxial screw is made of titanium or some other biocompatible metal. Being made of metal allows the doctor to view the bone screw using X-ray photographs during and after implantation.
However, because the bone screws are made of metal, the screws block X-rays passing through the body, in effect obscuring adjacent bone and other X-ray viewable internal structures surrounding the area and thereby preventing the surgeon from viewing those structures on an X-ray photograph. This can limit a surgeon's ability to ensure proper placement of the bone screw and diagnose and treat problems that arise near the location of the bone screw after the bone screw has been implanted.
Accordingly, what is needed are polyaxial and fixed bone screws that overcome some or all of the above disadvantages.